Each card features: - 5 holes (one at each corner and one in the center) which are easily identified by a letter (A,B,C,D) associated with the four outer holes - an asymmetric etched design which makes it easy to check whether all your cards are in the same orientation (as shown in the listing photos) - a different number of etched lines for each side of each card which makes it easy to keep track of where you are in your pattern when looking down onto your cards (as shown in the listing photos).